[openib-general] IB: I don't like what I'm seeing.

Thu Apr 1 07:13:20 PST 2004

On Wed, 31 Mar 2004, Tillier, Fabian wrote:

> So back on the topic of UD vs. RC, if you have to do SW checksum anyway,
> is there something to be gained in having the ability of doing HW
> assisted large sends, RMDA, etc for the large scale HPC environment?

we do RDMA now on HIPPI 800 and it is fine. But we still do a software 
checksum. 

RDMA is not the same thing as zero-copy, though everyone seems to want to 
treat it that way. 

> Does the assumption that the application is the only thing that can give
> you end-to-end data integrity remove all value provided by RC/UC
> services and RDMA?  Does the IB RC service have issues beside the lack
> of reliability?

RC looks to be a real headcache for large clusters. Having seen the stack 
I would much prefer the 'scrape it clean and give me packets' approach. 

ron

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